Some of the earlier prior art in this area includes U.S. Pat. Nos. 3,646,715 and 3,715,417 (Pope) assigned to Dupont of Canada and U.S. Pat. No. 3,740,909 (Stinnes) to the same Assignee.
This invention relates to a prefabricated composite building panel of the type comprising a rigid foam sheet of foamed cellular polymeric material, such as polyurethane or the like, on an outer face of which is attached a plurality of facing elements, such as brick slices, which are partially embedded in and attached to the outer face by the foaming action of the polymeric material. The facing elements are arranged in a pattern with spaces between the facing elements with those spaces being filled by a covering layer on the outer face of the foam sheet which is preferably formed of an aggregate intimately bonded into or integrated with the outer face of the foam sheet by the foaming action of the polymeric material. The basic model of this type of building panel is best outlined in our issued U.S. Pat. No. 5,715,637 to Hesterman et al.
All of these patents relate to a system of manufacturing prefabricated composite panels which has achieved some commercial success. One point which has to some extent limited commercial success is that of a restriction in the fire retardant qualities of the product. The brick facing elements are of course resistant to combustion. The aggregate which is embedded into the outer layer of the polyurethane foam sheet is also resistant to combustion. However the polyurethane foam itself is combustible and hence there is some possibility of the panel as a whole reaching a state of combustion so that the panel breaks down allowing direct access by the flame to the foam which can then bum freely eventually allowing access to the wall structure behind the panel.
Combustion tests have been observed and it has been found that once the aggregate layer filling the spaces between the facing elements has been breached by the combustion, rapid combustion of the polyurethane foam behind the facing elements and the aggregate soon occurs thus causing breakdown of the panel. Thus the panel is resistant to combustion for an initial period of time but once the layer is breached then the breakdown of the panel soon follows.